spi: imx: Three fixes for the i.MX SPI driver

John Madieu <john.madieu@gmail.com> says:

This series independent fixes found in the i.MX SPI driver.

These are:

1/3 fixes a precedence bug in spi_imx_dma_max_wml_find() that makes
    the watermark-finding logic effectively dead code. The function
    currently always returns wml = 1 because of how the !-operator
    binds to the modulo expression.

2/3 fixes a missing return on the package-1 failure path in
    spi_imx_dma_data_prepare(). The error path frees the
    dma_data array and the package-0 buffers, then falls through
    to "return 0" - the caller proceeds with a freed pointer.

3/3 makes spi_imx_setupxfer() propagate the prepare_transfer()
    return value. Currently a -EINVAL from mx51_ecspi_prepare_transfer
    (e.g. on a word_delay overflow) is silently swallowed and the
    transfer proceeds with a partially-configured controller.